A scrap-book of elementary mathematics; notes, recreations, essays (1908)
White, William Frank, 1871- · Chicago, The Open Court Pub. Co · leaf 197
l88 A SCRAP-BOOK OF ELEMENTARY MATHEMATICS. Place the numbers 1 to 19 on the sides of the equi- lateral triangles so that the sum on every side is the same. … The sum on the sides of the triangles in Fig. 51 is 22. In Fig. 52 it is 23. If we subtract each of the above numbers from 20, we have solutions where the sums are respectively 38 and 37.
Mathematical recreations
Internet Archive · Cornell University Library · Public domain (published before 1931). Free to use for anything.
